Researchers have developed an improved method for performing sentinel lymph node biopsy, a crucial first step in determining whether a cancer has spread to other parts of the body. The new method depends on quantum dots, nanometer-sized crystals that emit near-infrared light, to illuminate lymph nodes during cancer surgery. The research, resulting from collaboration between researchers at MIT, Beth Israel Deaconess Medical Center and Brigham and Women’s Hospital, will be published in the January issue of Nature Biotechnology.
The new near infra-red quantum dots were developed and synthesized at the MIT department of chemistry in the laboratory of Professor Moungi Bawendi, a scientific co-founder and advisory board member of Quantum Dot Corporation (QDC). The novel intraoperative, near-infrared fluorescence imaging system was developed in the laboratory of Dr. John Frangioni, Assistant Professor of Medicine and Radiology at Harvard Medical School and an Attending Physician at Beth Israel Deaconess Medical Center.
The study, entitled “Near-Infrared Fluorescent Type-II Quantum Dots for Sentinel Lymph Node Mapping,” by Sungjee Kim, and colleagues, describes how the quantum dots were injected into live pigs and followed visually to the lymph system just beneath the skin of the animals. The new imaging technique allowed the surgeons to clearly see the target lymph nodes without cutting the animals’ skin.
Sentinel Lymph Node (SLN) mapping, the surgical technique employed in the study, is a common procedure used to identify the presence of cancer in a single, “sentinel” lymph node, thus avoiding the removal of a patient’s entire lymph system. SLN mapping relies on a combination of radioactivity and organic dyes but the technique is inexact during surgery, often leading to removal of much more of the lymph system than necessary, causing unwanted trauma. The current work was performed on laboratory animals, including near-human sized pigs, considered by scientists to be a good predictor of human results.
The study reported that the new imaging system with near-infrared quantum dots was a significant improvement over the dye/radioactivity method currently used to perform SLN for several reasons, including:
- Throughout the procedure, the quantum dots were clearly visible using the imaging system, allowing the surgeon to see not only the lymph nodes, but also the underlying anatomy.
- The imaging system and quantum dots allowed the pathologist to focus on specific parts of the SLN that would be most likely to contain malignant cells, if cancer were present.
- The imaging system and quantum dots minimized inaccuracies and permitted real-time confirmation of the total removal of the target lymph nodes, drastically reducing the potential for repeated procedures.
“SLN mapping has already revolutionized cancer surgery. Near-infrared quantum dots have the potential to improve this important technique even further,” said Dr. Frangioni.
“This is an impressive study,” added Carol Lou, president of QDC. “While still several years away from being a reality for patients, this is a wonderful demonstration of the potential of quantum dot nanotechnology to significantly enhance medical care.”